Thousands of Russians have marched through Moscow to mark two years since opposition leader Boris Nemtsov was gunned down outside the Kremlin.
Mr Nemtsov, a former deputy prime minister, was a fierce critic of President Vladimir Putin.
His February 27 2015 death, in what appeared to be a contract killing, sparked an outpouring of anger and fear in Russia's beleaguered opposition movement.
The memorial protest was the largest opposition gathering since a similar march for Mr Nemtsov in 2016.
Organisers put the number of participants at just over 15,000.
The police, known for underestimating attendance at political rallies, said about 5,000 people showed up.
"It's very important that after two years people continue to come out and show their solidarity with the ideas for which Boris Nemtsov fought for and gave his life," opposition activist Ilya Yashin, who was Mr Nemtsov's friend and colleague, told the Interfax news agency.
Demonstrators carried Russian flags, banners of opposition political parties and placards with quotes from Mr Nemtsov, including "If there's Putin, there's no Russia", and "Our only chance left is the street."
Some carried cardboard Russian flags with bullet holes in them.
"For us, Nemtsov represents free-thinking Russia and the democratic values for which we strive: free elections and no corruption," participant Yekaterina Getgarts said.
Five men went on trial for Mr Nemtsov's murder in a Moscow military court last year, but no verdicts have been returned in the ongoing case.
Investigators allege that the man who shot Mr Nemtsov was Zaur Dadayev, a former officer in an elite Chechen police unit.
But Mr Nemtsov's family and friends say it was a political hit with a trail that leads to senior officials in the North Caucasus republic of Chechnya who have not been charged or even questioned.
The Moscow rally largely passed without incident, but an unknown assailant threw green dye in the face of opposition leader Mikhail Kasyanov. Police made several arrests.
"This is the hysteria of the government. They do not know what to do. The government is afraid," opposition activist Gennady Gudkov, a former deputy in the lower house of parliament, said of the attack on Mr Kasyanov.
While large crowds are rare at opposition demonstrations in Mr Putin's Russia, the attendance at Sunday's rally was significantly lower than a year ago, when organisers estimated almost 25,000 people joined a Nemtsov memorial march.
Russia's opposition has been fragmented in recent years by pressure from the Kremlin, the flight abroad of leading activists and political infighting.
After the march, thousands of people laid flowers on the bridge where Mr Nemtsov was shot in the back several times while walking home with his girlfriend.
Similar demonstrations took place on Sunday in other Russian cities, including St Petersburg and Mr Nemtsov's hometown of Nizhny Novgorod.
Several thousand people participated in St Petersburg, but the turnout was low elsewhere.